# Developing the Negative

Photography I · The Black-and-White Analogue Laboratory · https://tryals.app/learn/photography-i/developing-the-negative

## What Is in a Developer

A **Developer** formula balances four components:

| Component | Typical chemical | Job |
|---|---|---|
| **Developing agent** | Metol, hydroquinone | Reduces exposed silver halide to silver |
| **Preservative** | Sodium sulfite | Protects solution from oxidation by air |
| **Accelerator or alkali** | Sodium carbonate, borax | Raises pH to activate the agent |
| **Restrainer** | Potassium bromide | Suppresses fog on unexposed grains |

Classic formulas use **superadditivity**, pairing two agents that work faster together. Kodak **D-76** is the industry standard metol-hydroquinone formula. Agfa **Rodinal** is a single-agent formula used at high dilutions for high acutance.

### Dilution

The notation 1+31 means 1 part concentrate to 31 parts water. **The** working mix has **thirty-two parts in total**. To make 640 ml, divide 640 by 32. You use 20 ml concentrate and 620 ml water.

### Time, Temperature, and Agitation

The standard processing temperature is **20 degrees Celsius**. Development times change with temperature:

| Temperature | Multiplier on the 20-degree time |
|---|---|
| 18 °C | 1.20 |
| 20 °C | 1.00 |
| 22 °C | 0.85 |
| 24 °C | 0.72 |

**Agitation** brings fresh chemistry to the emulsion. Invert for the first 10 seconds, then invert for 10 seconds every minute.

### The Sequence

* **Stop bath**: halts development instantly by lowering pH.
* **Fixer**: removes unexposed silver halides to clear the negative.
* Wash and dry.

> **Common pitfall:** ignoring temperature drift. A shift of just 4 degrees Celsius alters development time by nearly thirty per cent. Always monitor temperature continuously.

## Practice questions

7 of this lesson's 14 practice questions, with answers. The full set is in the app.

### 1. Arrange the stages of processing a black-and-white film in the order they are carried out.

**Answer:**

1. Developer
2. Stop bath
3. Fixer
4. Wash
5. Wetting agent
6. Dry

**Why:** The order is not negotiable and each step exists because the previous one has to be stopped or removed. The wetting agent is the one that looks optional and is not: without it the wash water dries in droplets and leaves marks that no amount of subsequent washing removes.

Page: https://tryals.app/practice/photography-i/developing-the-negative/arrange-the-stages-of-processing-a-black-and-white-film-in-the-order

### 2. Metol and hydroquinone together develop faster than the sum of their separate rates.

**Answer:** True

**Why:** **True**: this is **superadditivity**, and it is why almost every classic developer pairs two agents. The more active agent does the reducing and the second regenerates it in situ, so the pair sustains a rate that neither could hold alone. Phenidone and hydroquinone behave the same way.

Page: https://tryals.app/practice/photography-i/developing-the-negative/metol-and-hydroquinone-together-develop-faster-than-the-sum-of-their

### 3. An alkaline environment activates the developing agent, yet an acid stop bath is introduced immediately afterwards. Why does this sudden shift in pH bring chemical development to a halt?

A. It oxidises the preservative so that the solution spoils instantly
B. It dissolves the silver halides before they can turn into silver
C. It quickly neutralises the accelerator that energises the agent
D. It converts the restrainer into an active fog-producing chemical

**Answer:** C. It quickly neutralises the accelerator that energises the agent

**Why:** Development requires an alkaline pH maintained by the accelerator to reduce silver halides; dropping the pH neutralises this activation without stripping unexposed halides, which remains the fixer's task.

Page: https://tryals.app/practice/photography-i/developing-the-negative/an-alkaline-environment-activates-the-developing-agent-yet-an-acid

### 4. Complete the account of the developer and the sequence.

**Answer:** The component that suppresses development of unexposed grains and controls fog is the **restrainer**. The effect by which two agents together develop faster than the sum of their separate rates is called **superadditivity**. The fixer dissolves undeveloped halides by forming soluble **silver-thiosulfate** complexes. The standard processing temperature is **20** degrees Celsius.

**Why:** The third blank is the chemistry that makes photography possible at all. Silver halides are insoluble in water, and thiosulfate works because it forms complexes with silver that are not, which is why exhausted fixer, already loaded with silver, stops working long before it looks any different.

Page: https://tryals.app/practice/photography-i/developing-the-negative/complete-the-account-of-the-developer-and-the-sequence

### 5. Why does a film developed with no agitation at all show streaks running down from the dense areas? Select every statement that is part of the reason.

A. Developer at the emulsion surface is exhausted locally and is not replaced
B. The exhausted solution flows downward across the film below a dense area
C. The emulsion swells unevenly when it is not moved through the bath
D. The products of development are denser than the fresh solution and sink

**Answer:** A. Developer at the emulsion surface is exhausted locally and is not replaced; B. The exhausted solution flows downward across the film below a dense area; D. The products of development are denser than the fresh solution and sink

**Why:** The fourth is not what happens. The mechanism is purely a matter of flow: development exhausts the solution locally, the exhausted solution is denser and sinks, and the film below a dense area is therefore developed in weakened solution. Agitation exists to break that flow.

Page: https://tryals.app/practice/photography-i/developing-the-negative/why-does-a-film-developed-with-no-agitation-at-all-show-streaks

### 6. A film needs 10 minutes at 20 degrees Celsius. Using the multiplier table, how many minutes does it need at 24 degrees?

**Answer:** 7.2 (within ±0.5)

**Why:** **About 7.2 minutes**, or 7 minutes 12 seconds. Four degrees costs nearly thirty per cent of the time, which is why a thermometer checked once at the start of a session and never again is one of the commonest causes of unaccountably dense negatives on a warm afternoon.

Page: https://tryals.app/practice/photography-i/developing-the-negative/a-film-needs-10-minutes-at-20-degrees-celsius-using-the-multiplier

### 7. An acid stop bath does nothing that a plain water rinse does not also do.

**Answer:** False

**Why:** **False.** A water rinse dilutes the developer and slows it; an acid stop bath drops the pH and halts it immediately, which matters most for short development times. It also neutralises the alkali that would otherwise be carried into the fixer and exhaust it early.

Page: https://tryals.app/practice/photography-i/developing-the-negative/an-acid-stop-bath-does-nothing-that-a-plain-water-rinse-does-not-also